1. Field of the Invention
The present invention relates to improved means of testing human and animal subjects for the presence of certain malignancies. More specifically, an embodiment is disclosed that permits the diagnosis of several types of lymphoid malignancies (leukemias).
2. Detailed Discussion of Background and Prior Art
The inventor has discovered that blood sera and other body fluids collected from mice or human subjects with certain malignancies contain certain unique double-stranded DNA molecules, which have the ability to selectively inhibit certain members of the group of enzymes known as DNA polymerases. These DNA molecules are absent from sera obtained from mice or human subjects who do not have these malignancies. The inventor has, with others, described this discovery and these DNAs, with related information, in a series of papers. See: Perisco and Gottlieb, DNA Polymerases of Myeloma, Nature New Biology 239: 173-76 (1972); Gottlieb, Smith, Plescia, Perisco, and Nicholson, Inhibitor of DNA Polymerase, Nature 246: 480-82 (1973); Gottlieb, Smith, Plescia, Nicholson, Bowers, Pankuch, and Berkoben, An Inhibitor of DNA Polymerase, in Fundamental Aspects of Neoplasia, ch. 20, pp. 269-77 (1975); Gottlieb, Gottlieb, and Nicholson, Inhibition of DNA Polymerase by Sera, in Bibliotheca Haematologica, No. 43 (Basel 1976); Brennessel, Buhrer, and Gottlieb, Use of Insoluble Heparin for Isolation of DNA Polymerase, Analytical Biochemistry 87: 411- 17 (1978); Gottlieb, Chang, Buhrer, and Brennessel, Isolation from Murine Myeloma and Leukemia Cells of a Selective Inhibitor of DNA Polymerase, Cancer Research 40: 758-70 (1980). These DNAs are referred to herein collectively as "DNA-L".
DNA-L is a mixture of DNA molecules in the 150 to 300 base pair range. Any of these DNA molecules can selectively inhibit R-1 DNA polymerase. The inventor has separated these DNA molecules into two groups, DNA-1 and DNA-2, which can be separated by chromatography. Similar DNA molecules can be extracted from normal liver, but not from normal blood sera. Normal blood sera lack these DNAs, and sera of patients with leukemia have the DNAs. All of the foregoing DNA-L molecules can be cloned and used in the test procedures described herein.
There are two groups of DNA-L molecules of principal interest herein, each of which contains a limited but undetermined number of different molecules. The DNAs of principal interest herein may be termed "DNA-1" and "DNA-2." It is believed that these DNAs may play an important role in the replication of leukemic cells. DNA-1 and DNA-2 have important common properties.
Both DNA-1 and DNA-2 have been demonstrated to exert selective inhibition for R-1 DNA polymerase enzyme, which is found in murine myeloma and may exist in other tumors and normal tissues. (The inhibition is "selective," in that other DNAs may well exist that will indiscriminately inhibit this and other polymerase enzymes. The DNAs of interest inhibit the R-1 DNA polymerase and do not inhibit other known polymerase enzymes.) The R-1 DNA polymerase enzyme may be recovered from murine MOPC-21 myeloma tumor by procedures described in Analytic Biochemistry 87: 411-17 (1978), supra. The fact that the enzyme is of murine origin is immaterial, because it reacts with DNAs of interest from both human and murine sources.
Present tests for leukemia, such as bone marrow tests, may be inconvenient and traumatic for the patient. Also, their sensitivity is limited to detecting the presence of substantial numbers of cancer cells, so that early cases of leukemia may escape detection. The procedures of this invention do not involve production of antibodies, as in the work of Bogoch, Detection of Malignant Tumor Cells, U.S. Pat. No. 4,298,590 (Nov. 3, 1981). Such laborious and indirect methods of measurement are not used herein.